Absorbing termination in an interconnect

ABSTRACT

Embodiments of the present disclosure are directed toward techniques and configurations for electrical signal absorption in an interconnect disposed in a printed circuit board (PCB) assembly. In one instance, a PCB assembly may comprise a substrate, and an interconnect formed in the substrate to route an electrical signal within the PCB. The interconnect may be coupled with a connecting component that is disposed on a surface of the PCB. An absorbing material may be disposed on the PCB to be in direct contact with at least a portion of the connecting component to at least partially absorb a portion of the electrical signal. Other embodiments may be described and/or claimed.

FIELD

Embodiments of the present disclosure generally relate to the field ofprinted circuit board design, and more particularly, to techniques andconfigurations for reducing reflected noise signals in connectors usedin the printed circuit boards and/or terminating signals in cross-talkmeasurements.

BACKGROUND

Electric signals within multilayered printed circuit boards (PCBs),silicon dies, or package substrates are routed through interconnects,such as vias, connectors, transmission lines, and the like. Someinterconnects may have connecting components, such as routing vias,ports, or connectors such as slots used for memory modules or memorycards. In some instances, undesired effects related to reflection ofelectrical signals may occur in interconnects. For example, not allconnectors (e.g., memory module slots) disposed on a PCB may be in use,and some connectors may remain empty. Accordingly, electrical signalsrouted to the connectors may create undesired reflected noise signals inthe empty connectors, which may negatively affect signaling performanceof the PCB. For example, the reflected noise signals occurring in theempty connectors may distort desired signals passing through theoccupied connectors and decrease the usable bandwidth of theinterconnect.

In some instances, transmission lines in the PCBs may be tested (e.g.,measured) for undesired effects caused by reflected noise signals, suchas the effect known as cross-talk. In conventional measurementtechniques, termination of electric signals used for measurements may beprovided by using resistive termination. However, resistive terminationmay be difficult to implement. For example, connecting the resistors toprecise positions on a transmission line disposed in a PCB may betime-consuming, costly, and often ineffective.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be readily understood by the following detaileddescription in conjunction with the accompanying drawings. To facilitatethis description, like reference numerals designate like structuralelements. Embodiments are illustrated by way of example and not by wayof limitation in the figures of the accompanying drawings.

FIG. 1 illustrates a schematic diagram of an example printed circuitboard (PCB) assembly, in accordance with some embodiments.

FIG. 2 schematically illustrates a signaling diagram of a PCB assemblyhaving an interconnect of FIG. 1, in accordance with some embodiments.

FIG. 3 illustrates a cross-section view of an example connectingcomponent of an interconnect of FIGS. 1-2 coupled with a PCB assembly,in accordance with some embodiments.

FIG. 4 is an example schematic diagram for signal measurements in a PCBassembly, in accordance with some embodiments.

FIG. 5 is another example schematic diagram for signal measurements in aPCB assembly, in accordance with some embodiments.

FIG. 6 is another example schematic diagram for signal measurements in aPCB assembly, in accordance with some embodiments.

FIGS. 7-10 illustrate perspective views of example implementations ofabsorbing terminators formed from absorbing materials in a PCB assemblyconfigured for signal measurements as described in reference to FIGS. 4and 6, in accordance with some embodiments.

FIG. 11 is a process flow diagram for providing an absorbing material toan interconnect in a PCB assembly, in accordance with some embodiments.

FIG. 12 schematically illustrates a computing device including a PCBassembly in accordance with some embodiments.

DETAILED DESCRIPTION

Embodiments of the present disclosure describe techniques andconfigurations for electrical signal reflection and/or absorption forinterconnects formed in a substrate of a printed circuit board (PCB) toroute an electrical signal within the PCB. The interconnect may includea connecting component that may be at least partially disposed on asurface of the PCB, and an absorbing material that may be disposed to bein direct contact with at least a portion of the connecting component toat least partially absorb a portion of the electrical signal.

To provide the desired absorption level, the absorbing material may beselected to satisfy certain conditions. For example, a desiredabsorption may be achieved when the absorbing material has a dielectricloss tangent that is greater than one for a frequency range of theresonant frequency of the reflected signal and a dielectric constantthat is inversely proportional to the frequency of the reflected signal.

The described techniques invention provide several advantages overresistive terminations. For example, the described embodiments allowsthe termination to be operated without permanently adding components,and for more robust de-embedding or calibration to be designed. Thetermination created with absorbing material may be more flexible androbust than resistive termination. The absorbing material may becommercially available in different states: foam, plastic,adhesive/glue, type, film, etc.

The described embodiments may provide desirable wideband termination,which is the key for high speed measurement. The termination created byabsorbing material may perform better than that by resistive terminationin high frequency and high speed region. Broadband absorbing materials,which have excellent absorption over broadband microwave and millimeterfrequencies, have been commercially available.

The described embodiments may also provide narrowband or half-bandtermination, which are desirable for some special characterizationmeasurements. Narrowband absorbers have also been commercially availableand provide decent narrowband or half-band termination.

In the following description, various aspects of the illustrativeimplementations will be described using terms commonly employed by thoseskilled in the art to convey the substance of their work to othersskilled in the art. However, it will be apparent to those skilled in theart that embodiments of the present disclosure may be practiced withonly some of the described aspects. For purposes of explanation,specific numbers, materials, and configurations are set forth in orderto provide a thorough understanding of the illustrative implementations.However, it will be apparent to one skilled in the art that embodimentsof the present disclosure may be practiced without the specific details.In other instances, well-known features are omitted or simplified inorder not to obscure the illustrative implementations.

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, wherein like numeralsdesignate like parts throughout, and in which is shown by way ofillustration embodiments in which the subject matter of the presentdisclosure may be practiced. It is to be understood that otherembodiments may be utilized and structural or logical changes may bemade without departing from the scope of the present disclosure.Therefore, the following detailed description is not to be taken in alimiting sense, and the scope of embodiments is defined by the appendedclaims and their equivalents.

For the purposes of the present disclosure, the phrase “A and/or B”means (A), (B), or (A and B). For the purposes of the presentdisclosure, the phrase “A, B, and/or C” means (A), (B), (C), (A and B),(A and C), (B and C), or (A, B, and C).

The description may use perspective-based descriptions such astop/bottom, in/out, over/under, and the like. Such descriptions aremerely used to facilitate the discussion and are not intended torestrict the application of embodiments described herein to anyparticular orientation.

The description may use the phrases “in an embodiment,” or “inembodiments,” which may each refer to one or more of the same ordifferent embodiments. Furthermore, the terms “comprising,” “including,”“having,” and the like, as used with respect to embodiments of thepresent disclosure, are synonymous.

The term “coupled with,” along with its derivatives, may be used herein.“Coupled” may mean one or more of the following. “Coupled” may mean thattwo or more elements are in direct physical or electrical contact.However, “coupled” may also mean that two or more elements indirectlycontact each other, but yet still cooperate or interact with each other,and may mean that one or more other elements are coupled or connectedbetween the elements that are said to be coupled with each other. Theterm “directly coupled” may mean that two or more elements are in directcontact.

In various embodiments, the phrase “a first layer formed, deposited, orotherwise disposed on a second layer” may mean that the first layer isformed, deposited, or disposed over the second layer, and at least apart of the first layer may be in direct contact (e.g., direct physicaland/or electrical contact) or indirect contact (e.g., having one or moreother layers between the first layer and the second layer) with at leasta part of the second layer.

As used herein, the term “module” may refer to, be part of, or includean Application Specific Integrated Circuit (ASIC), an electroniccircuit, a processor (shared, dedicated, or group), and/or memory(shared, dedicated, or group) that execute one or more software orfirmware programs, a combinational logic circuit, and/or other suitablecomponents that provide the described functionality.

The embodiments of the present disclosure will be described in referenceto FIGS. 1-3. The embodiments may include an apparatus comprising adielectric layer and an interconnect (e.g., formed in the dielectriclayer) to route an electrical signal through the dielectric layer, wherethe interconnect includes a connecting component on the interconnect,and at least a portion of the connecting component may be covered withan absorbing material to at least partially absorb a portion of theelectric signal (e.g., reflected noise signal). In some embodiments, theapparatus may comprise a PCB assembly, a die, a package substrate, or aprinted circuit board.

FIG. 1 illustrates a schematic diagram of an example printed circuitboard (PCB) assembly 100, in accordance with some embodiments. The PCBassembly 100 may comprise a substrate 102. The substrate 102 may be asubstrate made of dielectric material including, for example, build-uplayers (not shown) configured to route electrical signals through thePCB assembly 100. The PCB assembly 100 may include one or moreinterconnects (such as interconnect 104) configured to route electricalsignals 106 such as, for example, input/output (I/O) signals and/orpower or ground signals associated with the operation of the PCBassembly 100. In some embodiments, the interconnect 104 may comprise avia filled with a conductive material, such as copper, to provide forelectrical conductivity for the incoming signal 106.

The interconnect 104 may further comprise one or more connectingcomponents 130, 132 that may be disposed on a surface of the PCBassembly 100, e.g., on a surface of the substrate 102. In someembodiments, an absorbing material may be disposed to be in directcontact with at least a portion of the connecting component 130 or 132to at least partially absorb a portion of the electrical signaltraveling through the interconnect 104, as will be described below ingreater detail.

In some embodiments, the interconnect 104 may comprise one or moretransmission lines coupled with connecting components 130, 132 (e.g.,ports) that may be at least partially disposed on the surface of thesubstrate 102, as will be discussed in greater detail in reference toFIGS. 4-10.

In some embodiments, the connecting components 130, 132 may compriseconnector slots configured to receive corresponding connecting elementsof respective computing components (e.g., receiver 124) to be coupledwith the PCB assembly 100. The computing components may comprise varioustypes of components of a computing device or system that may be coupledto the PCB assembly 100, via the connecting components 130, 132. Forexample, the computing component (e.g., receiver) 124 may comprise amemory module, such as a dual in-line memory module (DIMM), to receiveand store data comprising the electrical signal 106 routed within thePCB assembly 100. As known, the computing component 124, such as a DIMM,may have a connecting element (not shown) configured to be insertable inthe connecting component (slot) 130, to couple the computing component124 with the PCB assembly 100.

In some embodiments, the incoming signal 106 may be routed via anelectrically conductive trace (e.g., transmission line 110) into theinterconnect 104, to the receiver 124 (e.g., memory module or othercomputing component) via another electrically conductive line 112, asshown. Accordingly, the incoming signal 106 may be split into twoportions. One portion, a desired transmission signal 118, may travel toa receiving point via the conductive line 112, while another portion 120may continue traveling through a conductive line 122 of the interconnect104, forming a reflected noise signal 123, reflected off the emptyconnecting component (slot) 132. The reflected noise signal 123 maycomprise surface waves and/or evanescent waves, and may include somepropagating waves. The reflected noise signal 123 may cause undesirableeffects for the interconnect 104, for example, distort desired signal118 passing through the line 112 to the receiver 124 and decrease theusable bandwidth of the interconnect 104.

To mitigate undesirable effects related to the reflected noise signal123, in some embodiments, a component 140 may be coupled with the PCBassembly 100 via the connecting component 132. In some embodiments, thecomponent 140 may comprise an insertable component, e.g., a computingcomponent. In some embodiments, the component 140 may comprise aninsertable component, such as, for example, a dummy module. Thecomponent 140 may have a connecting element 142 for insertion into theconnecting component (slot) 132, as indicated by arrow 160. Theconnecting element 142 of the insertable component 140 (e.g., dummymodule) may include absorbing material 150. For example, a layer ofabsorbing material 150 may be applied to the connecting element 142 toat least partially cover the contacts of the connecting elementinsertable into the connecting component (slot) 132. Accordingly, theconnecting component 132 may be covered with the absorbing material 150when the connecting element 142 of the component 140 (e.g., dummymodule) is inserted into the connecting component (slot) 132, such thatthe absorbing material 150 may be in direct contact with an insideportion 152 of the connecting component (slot) 132.

The absorbing material 150 covering at least a portion of the connectingcomponent 132 may at least partially absorb the reflected noise signal123 formed by the inbound signal 120 when reflected off the connectingcomponent 132, thus reducing inter-symbol interference (ISI) and harmfulcoupling, and correcting timing jitter that may be induced by thereflected noise signal 123. The reduction of the reflected noise signal123 using the absorbing material 150 may be particularly effective inhigh-speed signaling, e.g., at frequencies ranging from about 5 to 7GHz, such as for connecting component (slot) 132 being a DIMM connector.FIG. 2 schematically illustrates a signaling diagram 200 of a PCBassembly 100 having an interconnect 104, in accordance with someembodiments. The diagram 200 illustrates the elements of theinterconnect 104 in greater detail. It is assumed that the signal 106may be generated by a central processing unit 204, which for purposes ofsimplicity may considered as a transmitter of the signal 106 via theinterconnect 104, to be received by a computing component 224 (e.g.,receiver 124 such as a memory module). (Conversely, the centralprocessing unit 204 may be a receiver of a signal transmitted by thecomputing component 224 via the interconnect 104. However, the principleof the described embodiments remains the same.) In some embodiments, thePCB assembly 100 may comprise a motherboard of a computing system.

As shown, the signal 106 may travel through various components of theinterconnect 104, including socket 206, one or more vias 208, breakout210 (e.g., channel transmission or receiver signal routing components),open route 212 (e.g., regular PCB routing outside of the special routingareas such as breakout, pinfield, etc.), pinfield 214 (e.g., a PCB areawhere multiple dense pins may be disposed, such as, for example, the PCBarea underneath the connector), and interconnect elements 216 and 218(e.g., DIMM-DIMM in case the computing component 224 insertable inconnecting component 130 and corresponding computing component (e.g.,140) insertable in connecting component 132 may comprise DIMM).

As described in reference to FIG. 1, if connecting component 132 remainsempty in the above configuration, a component 140 (e.g., dummy module)with connecting element 142 covered with absorbing material may beinserted 280 into the connecting component 132, in order to at leastpartially absorb a portion of the incoming signal 106 traveling toward132, and substantially reduce the reflected noise signal.

FIG. 3 illustrates a cross-section view 300 of an example connectingcomponent 132 coupled with a PCB such as PCB assembly 100, in accordancewith some embodiments. As shown, the connecting component 132 may becoupled with (e.g., mounted on a surface of) the substrate 102 of thePCB assembly 100. Some of the components of the interconnect 104 (e.g.,vias for providing electrical connection for an electrical signaltraveling through the PCB assembly 100) are also shown and denoted bynumeral 304. The connecting component 132 may include one or moreconnection elements 306, such as pins or gold finger contacts comprisingthe inside portion 152 of the connecting component 132.

As shown, a component 140, such as dummy module, may be inserted intothe connecting component 132, to provide a direct contact for absorbingmaterial 150 covering the connecting element 142 with the connectionelements 306, to at least partially absorb the inbound signal 120traveling through the interconnect 104 to the connecting component 132to reduce or substantially eliminate reflected noise (e.g., signal 123in FIG. 1.)

Besides the embodiments described in reference to FIG. 3, the absorbingmaterial 150 may be used to mitigate the undesired effects for othertypes of embodiments that may be used in PCB signaling and measurements,such as high-speed (e.g., 1 or 1.5 gigabits per second (Gbps) and above,such as for the double data rate (DDR) memory interfaces), which aredescribed in reference to FIGS. 4-10.

FIG. 4 is an example schematic diagram for signal measurements in a PCBassembly, in accordance with some embodiments. More specifically, FIG. 4illustrates an example schematic representation for far end cross-talk(FEXT) measurements in a PCB assembly. The schematic representation mayinclude an interconnect 400 disposed on a PCB (not shown).

The interconnect 400 may comprise a first transmission line 402 that mayinclude a connecting component 404. A first end 406 of the transmissionline 402 may be connected to a transmitter Tx (not shown) to transmit anelectrical signal 410 through the transmission line 402. In someembodiments, a second (far) end 412 of the transmission line 402 may bedisposed on the surface of the PCB to form a port for the electricalsignal 410 passing through the transmission line 402. Accordingly, thesecond (proximal) end 412 may comprise the connecting component 404(port). In some embodiments, the connecting component 404 (e.g., port)may be at least partially covered with the absorbing material to form anabsorbing terminator to provide substantial termination of theelectrical signal 410.

The interconnect 400 may further comprise a second transmission line 420disposed in proximity to the first transmission line 402. The secondtransmission line 420 may include a second absorbing terminator 422comprising a first end 424 of the second transmission line 420. Theabsorbing terminator 422 may be covered with the absorbing material aswill be described below in greater detail.

The first end 424 of the second transmission line 420 may be disposed inproximity to the first end 406 of the first transmission line 402. Asecond end 430 of the second transmission line 420 may be connected to areceiver Rx (not shown) of a signal 432 caused by magnetic interferencefrom the electric signal 410 passing through the first transmission line402. Accordingly, the schematic representation of interconnect 400including the first and second transmission lines 402 and 420 configuredas described above may enable FEXT measurements associated with theelectrical signal 410.

FIG. 5 is another example schematic diagram for signal measurements in aPCB assembly, in accordance with some embodiments. More specifically,FIG. 5 illustrates an example schematic representation for FEXT returnloss measurements in a PCB assembly. The schematic representation mayinclude an interconnect 500 disposed in the PCB (not shown).

Similarly to the embodiment described in reference to FIG. 4, theinterconnect 500 may comprise a first transmission line 502 that mayinclude a connecting component 504. A first end 506 of the transmissionline 502 may be connected to a transmitter Tx (not shown) to transmit anelectrical signal 510 through the transmission line 502. In someembodiments, a second (proximal) end 512 of the transmission line 502may be disposed on the surface of the PCB to form a port for theelectrical signal 510 passing through the transmission line 502.Accordingly, the second (proximal) end 512 may comprise the connectingcomponent 504 (port). In some embodiments, the connecting component 504(e.g., port) may be at least partially covered with the absorbingmaterial to form an absorbing terminator to provide substantialtermination of the electrical signal 510. A return loss signal 540resulting from discontinuity of the signal 510 may be received by areceiver Rx (not shown) connected to the first end 506 and measuredaccordingly.

The interconnect 500 may further comprise a second transmission line 520disposed in proximity to the first transmission line 502. The secondtransmission line 520 may include a second absorbing terminator 522comprising a first end 524 of the second transmission line 420. A thirdabsorbing terminator 528 may be disposed at a second end 530 of thesecond transmission line 520, to substantially terminate a signal 532caused by magnetic interference from the electric signal 510 passingthrough the first transmission line 502. The absorbing terminators 522and 528 may be covered with the absorbing material as will be describedbelow in greater detail. Accordingly, the schematic representation ofinterconnect 500 including the first and second transmission lines 502and 520 as described above may enable measurements of FEXT return lossassociated with the electrical signal 510.

FIG. 6 is another example schematic diagram for signal measurements in aPCB assembly, in accordance with some embodiments. More specifically,FIG. 6 illustrates an example schematic representation for near endcross-talk (NEXT) measurements in a PCB assembly. The schematicrepresentation may include an interconnect 600 disposed in the PCB (notshown).

Similarly to the embodiment described in reference to FIGS. 4 and 5, theinterconnect 600 may comprise a first transmission line 602 that mayinclude a connecting component 604. A first end 606 of the transmissionline 602 may be connected to a transmitter Tx (not shown) to transmit anelectrical signal 610 through the transmission line 602. In someembodiments, a second (proximal) end 612 of the transmission line 602may be disposed on the surface of the PCB to form a port for theelectrical signal 610 passing through the transmission line 602.Accordingly, the second (proximal) end 612 may comprise the connectingcomponent 604 (port). In some embodiments, the connecting component 604(e.g., port) may be at least partially covered with the absorbingmaterial to form an absorbing terminator to provide substantialtermination of the electrical signal 610.

The interconnect 600 may further comprise a second transmission line 620disposed in proximity to the first transmission line 602. The secondtransmission line 620 may include a second absorbing terminator 628comprising a first end 630 of the second transmission line 620. Thesecond absorbing terminator 628 may be covered with the absorbingmaterial to form an absorbing terminator to provide substantialtermination of the signal 632 caused by magnetic interference from theelectric signal 610 passing through the first transmission line 602. Asecond end 634 of the second transmission line 620 may be disposed inproximity to the first end 606 of the first transmission line 602 andconnected to a receiver Rx (not shown) of a signal 636 caused bymagnetic interference from the electric signal 610 passing through thefirst transmission line 602. Accordingly, the schematic representationof interconnect 600 including the first and second transmission lines602 and 620 configured as described above may enable measurements ofnear end cross-talk associated with the electrical signal 610.

FIGS. 7-10 illustrate perspective views of example implementations ofabsorbing terminators formed from absorbing materials in a PCB assemblyconfigured for signal measurements as described in reference to FIGS. 4and 6, in accordance with some embodiments. More specifically, FIGS. 7-8illustrate example implementations of absorbing terminators in a PCBassembly used for FEXT measurements, and FIGS. 9-10 illustrate exampleimplementations of absorbing terminators in a PCB assembly used for NEXTmeasurements.

FIG. 7 illustrates a perspective view of an example implementation ofthe schematic representation of the PCB assembly with the interconnect400 of FIG. 4, in accordance with some embodiments. The exampleimplementation may include a PCB assembly 700 including a substrate 702,on which an interconnect 704 similar to 400 may be disposed. As shown,some transmission lines of the interconnect 400 corresponding to lines402 and 420 (e.g., line 708) may be disposed on a first (e.g., top)surface 710 of the substrate 702, and others (e.g., 712) may be disposedon a second (e.g., bottom) surface 716 of the substrate 702. It will beappreciated that the above-described configuration of the interconnect700 is provided for illustration purposes only; other configurations(e.g., having one or more or all transmission lines on one surface ofthe substrate 702) are possible.

The measured ports 720 and 722 in FIG. 7 correspond to respective ends406 and 430 of the transmission lines 402 and 420 of FIG. 4, and theopen ports 724 and 726 correspond to respective ends 412 and 424 of thetransmission lines 402 and 420 of FIG. 4. In order to providetermination of signal traveling, e.g., in lines 712 and 708 torespective open ports 724 and 726, the absorbing terminators may beformed on the ports 724 and 726 as described in reference to FIG. 4.More specifically, absorbing material may be applied to the open ports724 and 726, as indicated by arrows 740 and 742, in order tosubstantially terminate the signals traveling to these ports.

FIG. 8 illustrates another perspective view of an example implementationof the schematic representation of the PCB assembly with theinterconnect 400 of FIG. 4, in accordance with some embodiments. Morespecifically, FIG. 8 illustrates an implementation of the schematicrepresentation of interconnect 400 similar to that of FIG. 7 showing thePCB assembly 700 with absorbing terminators 802 and 804 formed on theports 724 and 726 respectively. As shown, layers of absorbing material810 and 812 may be applied (e.g., attached) to the open ports 724 and726 on each side of the substrate 702, covering the ports to provideeffective termination of signals traveling to these ports. As shown, thelayers of absorbing material 810 and 812 may cover, at least partially,portions of transmission lines 708 and 712 (not visible in FIG. 8)around proximal ends of these lines that form the ports 724 and 726. Thelayers of absorbing material 810 and 812 may be applied to the substrate702 and retained in place in a number of different ways, including, butnot limited to, fastening, gluing, applying pressure, or other methodsknown in the art.

FIG. 9 illustrates a perspective view of an example implementation ofthe schematic representation of the PCB assembly with the interconnect600, in accordance with some embodiments. The example implementation mayinclude a PCB assembly 900 including a substrate 902, on which aninterconnect 904 similar to 600 may be disposed. As shown, sometransmission lines of the interconnect 900 corresponding to lines 402and 420 (e.g., line 907) may be disposed on a first (e.g., top) surface910 of the substrate 902, and others (e.g., 908, 912) may be disposed ona second (e.g., bottom) surface 916 of the substrate 902. It will beappreciated that the above-described configuration of the interconnect900 is provided for illustration purposes only; other configurations(e.g., having one or more or all transmission lines on one surface ofthe substrate 902) are possible.

The measured ports 920 and 922 in FIG. 9 correspond to respective ends606 and 634 of the transmission lines 602 and 620 of FIG. 6, and theopen ports 924 and 926 correspond to respective ends 612 and 630 of thetransmission lines 602 and 620 of FIG. 6. In order to providetermination of signal traveling, e.g., in lines 912 and 908 torespective open ports 924 and 926, the absorbing terminators may beformed on the ports 924 and 926 as described in reference to FIG. 6.More specifically, absorbing material may be applied to the open ports924 and 926, as indicated by arrows 940 and 942, in order tosubstantially terminate the signals traveling to these ports.

FIG. 10 illustrates another perspective view of an exampleimplementation of the schematic representation of the PCB assembly 900with the interconnect 600 of FIG. 6, in accordance with someembodiments. More specifically, FIG. 10 illustrates an implementation ofa schematic representation similar to that of FIG. 9 showing the PCBassembly 900 with absorbing terminators 1002 and 1004 formed on theports 924 and 926 respectively. As shown, at least one layer ofabsorbing material 1010 may be applied (e.g., attached) to the openports 924 and 926 on the surface 916 of the substrate 902, covering theports 924 and 926 to provide effective termination of signals travelingto these ports. As shown, the layer of absorbing material 1010 maycover, at least partially, portions of transmission lines 908 and 912(not visible in FIG. 10) around proximal ends of these lines that formthe ports 924 and 926. The layer of absorbing material 1010 may beapplied to the substrate 902 and retained in place in a number ofdifferent ways, including, but not limited to, fastening, gluing,applying pressure, or other methods known in the art.

In some embodiments, the absorbing material (e.g., 150, 810, 812, and/or1010 referenced above) may be selected so as to cause the reflectednoise signal (e.g., 123) comprising, e.g., electromagnetic wavesentering the absorbing material to attenuate quickly and dissipate asheat, thus reducing or eliminating the reflected noise signal. The wavepropagation factor for electromagnetic wave of the reflected noisesignal may be derived as follows.

The electromagnetic wave number in vacuum (free space) may be defined as

$k_{0} = \frac{2\pi}{\lambda_{0}}$

where k₀ and λ₀ are the electromagnetic wave number and wavelength invacuum. The electromagnetic wave number in media k (e.g., absorbingmaterial with relative permittivity {tilde over (∈)}_(r) and relativepermeability {tilde over (μ)}_(r)) may be written as

k=k ₀√{square root over (μ_(r)∈_(r))}

Since {tilde over (∈)}_(r)=∈_(r) (1+j tan δ), where tan δ is losstangent of the absorbing material, δ is the angle of loss tangent, ∈_(r)is the relative dielectric constant of the absorbing material, andnon-magnetic material permeability {tilde over (μ)}_(r)=1, theelectromagnetic wave number k may be defined as k=k₀√{square root over(∈_(r)(1+j tan δ))}, where j is the imaginary unit.The wave propagation factor may be derived from a Maxwell equationfollowing the following sequence of expressions:

${\exp \left( {j\; {kd}} \right)} = {\exp \left( {j\; {dk}_{0}\sqrt{ɛ_{r}\left( {1 + {j\; \tan \; \delta}} \right)}} \right)}$or${\exp \left( {j\; {kd}} \right)} = {\exp \left( {j\; d\frac{2\pi}{\lambda_{0}}\sqrt{ɛ_{r}\left( {1 + {j\; \tan \; \delta}} \right)}} \right)}$

where d is the distance of wave propagation inside the absorbingmaterial and λ₀ is wavelength of free space. The above expression may bewritten as follows:

${\exp \left( {j\; {kd}} \right)} = {\exp \left( {j\; d{\frac{2\pi}{\lambda_{0}}\left\lbrack {{{real}\left( \sqrt{ɛ_{r}\left( {1 + {{jtan}\; \delta}} \right)} \right)} + {j \cdot {{imag}\left( \sqrt{ɛ_{r}\left( {1 + {j\; \tan \; \delta}} \right)} \right)}}} \right\rbrack}} \right)}$  or${\exp \left( {j\; {kd}} \right)} = {\exp \left( {d{\frac{2\pi}{\lambda_{0}}\left\lbrack {{j\; {{real}\left( \sqrt{ɛ_{r}\left( {1 + {{jtan}\; \delta}} \right)} \right)}} - {{imag}\left( \sqrt{ɛ_{r}\left( {1 + {j\; \tan \; \delta}} \right)} \right)}} \right\rbrack}} \right)}$

The final expression may be written as follows:

${\exp \left( {j\; {kd}} \right)} = {{\exp \left( {j\; d\frac{2\pi}{\lambda_{0}}{{real}\left( \sqrt{ɛ_{r}\left( {1 + {j\; \tan \; \delta}} \right)} \right)}} \right)}{\exp \left( {{- d}\frac{2\pi}{\lambda_{0}}{{imag}\left( \sqrt{ɛ_{r}\left( {1 + {{jtan}\; \delta}} \right)} \right)}} \right)}}$

with loss factor being

${\exp \left( {{- d}\frac{2\pi}{\lambda_{0}}{{imag}\left( \sqrt{ɛ_{r}\left( {1 + {j\; \tan \; \delta}} \right)} \right)}} \right)}.$

Based on electromagnetic wave theory and the above expressions, thereflected waves may be ideally (fully) absorbed, if the absorbingmaterial satisfies the following conditions:

-   -   the loss tangent, tan δ, may be above one (>1) for a frequency        range of a resonant frequency of the reflected noise signal and,        in ideal conditions, may remain constant across the frequency        range;    -   the dielectric constant, ∈_(r), may be inversely proportional to        frequency, so that the loss factor may remain constant for the        frequency range of the frequency of the reflected noise signal.

The above requirements are formulated for ideal absorption (e.g.,elimination) of reflected noise signal by an absorbing material.Different types of absorbing materials with properties approximating orsatisfying the above conditions with desired threshold margins may beused to at least partially reduce or substantially eliminate reflectednoise signals in the interconnect stubs. For example, absorbingmaterials may be used that are produced by Cuming Microwave Corporation,MAST, Western Rubber and Supply, Inc., and the like. For example, CumingMicrowave Corporation's C-RAM MT-30 absorbing material may be used forthe purposes of at least partial absorption of a reflected noise signal.

FIG. 11 is a process flow diagram for applying an absorbing material toan interconnect in an apparatus, such as a PCB assembly, in order toprovide at least partial absorption of a portion of an electricalsignal, in accordance with some embodiments. The process 1100 maycomport with actions described in connection with FIGS. 1-10 in someembodiments.

At block 1102, one or more interconnects may be formed in a printedcircuit board (PCB) assembly to route electrical signals within the PCB.In some embodiments, the interconnects may comprise connectingcomponents, vias, transmission lines, or other types of interconnects,described in reference to FIGS. 1-3. In some embodiments, theinterconnect may include connecting components, transmission lines,vias, and ports described in reference to FIGS. 4-10. Forming theinterconnect may include disposing a connecting component of theinterconnect at least partially on a surface of the PCB. The connectingcomponent may comprise, for example, a slot described in reference toFIGS. 1-3 or a port described in reference to FIGS. 4-6.

At block 1104, an absorbing material may be applied to at least aportion of the connecting component, including providing a directcontact between the connecting component and the absorbing material, toat least partially absorb a portion of the incoming electrical signal,e.g., to reduce the reflected noise signals described in reference toFIGS. 1-3 or to substantially terminate signals described in referenceto FIGS. 4-6. Applying an absorbing material may include covering atleast portions of the connecting component with the absorbing materialas described in reference to FIGS. 1-6.

In some embodiments, prior to applying the absorbing material to theinterconnect stubs, the absorbing material may be selected according tothe criteria described above. For example, the absorbing material may beselected such that a dielectric loss tangent of the absorbing materialmay be greater than one, for a frequency range of a frequency of thereflected portions of the electric signals. The absorbing material maybe further selected such that a relative dielectric constant of theabsorbing material may be inversely proportionate to the frequency ofthe reflected portions of the electric signals.

At block 1106, the absorbing material may be retained in place, e.g., byfastening, gluing, applying pressure, or other methods.

FIG. 12 schematically illustrates a computing device 1200 including atleast a PCB assembly in accordance with some embodiments described inreference to FIGS. 1-11. The computing device 1200 may house a boardsuch as motherboard 1202. The motherboard 1202 may be implemented as thePCB assembly 100 described in reference to FIG. 1 or PCB assembliesdescribed in reference to FIGS. 4-6.

The motherboard 1202 may include a number of components, including butnot limited to a processor 1204 and at least one communication chip1206. One or more of the components in FIG. 12 shown as being attachedto the motherboard may be replaced by a connecting component comprisingabsorbing material.

The processor 1204 may be physically and electrically coupled to themotherboard 1202. In some implementations, the at least onecommunication chip 1206 may also be physically and electrically coupledto the motherboard 1202. In further implementations, the communicationchip 1206 may be part of the processor 1204.

Depending on its applications, computing device 1200 may include othercomponents that may or may not be physically and electrically coupled tothe motherboard 1202. These other components may include, but are notlimited to, volatile memory (e.g., dynamic random-access memory (DRAM))1220, non-volatile memory (e.g., read-only memory (ROM)) 1224, flashmemory 1222, a graphics processor 1230, a digital signal processor or acrypto processor (not shown), a chipset 1226, an antenna 1290, a display(e.g., touchscreen display) 1232, a touchscreen controller 1246, abattery 1236, a power amplifier 1241, a global positioning system (GPS)device 1240, a compass 1242, a speaker 1250, a camera 1252, a massstorage device (such as hard disk drive, compact disk (CD), or digitalversatile disk (DVD)), an audio codec, a video codec, a Geiger counter,an accelerometer, a gyroscope (not shown), and so forth.

In some embodiments, DRAM 1220 may include a computing component 124,such as memory module (e.g., DIMM) coupled with the processor 1204 viainterconnect 104 as described in reference to FIGS. 1-2. DRAM 1220 mayfurther include a computing component (e.g., dummy module) 140 withconnecting element 142 configured and connected to the interconnect 104via connecting component 132 of interconnect 104 as described inreference to FIGS. 1-3, to at least partially absorb reflected noisesignals.

In some embodiments, the computing device 1200 may be configured withinterconnects 400, 500, or 600, for signal measurements according to theembodiments described in reference to FIGS. 4-6. As described above, theinterconnects 400, 500, or 600 may include absorbing terminatorscomprising absorbing material as described in reference to FIGS. 7-10,to provide effective termination of electrical signals traveling throughportions of interconnects 400, 500, or 600.

The communication chip 1206 may enable wireless communications for thetransfer of data to and from the computing device 1200. The term“wireless” and its derivatives may be used to describe circuits,devices, systems, methods, techniques, communications channels, etc.,that may communicate data through the use of modulated electromagneticradiation through a non-solid medium. The term does not imply that theassociated devices do not contain any wires, although in someembodiments they might not. The communication chip 1206 may implementany of a number of wireless standards or protocols, including but notlimited to Institute for Electrical and Electronic Engineers (IEEE)standards including Wi-Fi (IEEE 802.11 family), IEEE 802.16 standards(e.g., IEEE 802.16-2005 Amendment), Long-Term Evolution (LTE) projectalong with any amendments, updates, and/or revisions (e.g., advanced LTEproject, ultra mobile broadband (UMB) project (also referred to as“3GPP2”), etc.). IEEE 802.16 compatible broadband wireless access (BWA)networks are generally referred to as WiMAX networks, an acronym thatstands for Worldwide Interoperability for Microwave Access, which is acertification mark for products that pass conformity andinteroperability tests for the IEEE 802.16 standards.

The communication chip 1206 may operate in accordance with a GlobalSystem for Mobile Communication (GSM), General Packet Radio Service(GPRS), Universal Mobile Telecommunications System (UMTS), High SpeedPacket Access (HSPA), Evolved HSPA (E-HSPA), or LTE network. Thecommunication chip 1206 may operate in accordance with Enhanced Data forGSM Evolution (EDGE), GSM EDGE Radio Access Network (GERAN), UniversalTerrestrial Radio Access Network (UTRAN), or Evolved UTRAN (E-UTRAN).The communication chip 1206 may operate in accordance with Code DivisionMultiple Access (CDMA), Time Division Multiple Access (TDMA), DigitalEnhanced Cordless Telecommunications (DECT), Evolution-Data Optimized(EV-DO), derivatives thereof, as well as any other wireless protocolsthat are designated as 3G, 4G, 5G, and beyond. The communication chip1206 may operate in accordance with other wireless protocols in otherembodiments.

The computing device 1200 may include a plurality of communication chips1206. For instance, a first communication chip 1206 may be dedicated toshorter range wireless communications such as Wi-Fi and Bluetooth, and asecond communication chip 1206 may be dedicated to longer range wirelesscommunications such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE, EV-DO, andothers.

The processor 1204 may refer to any device or portion of a device thatprocesses electronic data from registers and/or memory to transform thatelectronic data into other electronic data that may be stored inregisters and/or memory.

In various implementations, the computing device 1200 may be a laptop, anetbook, a notebook, an ultrabook, a smartphone, a tablet, a personaldigital assistant (PDA), an ultra mobile PC, a mobile phone, a desktopcomputer, a server, a printer, a scanner, a monitor, a set-top box, anentertainment control unit, a digital camera, a portable music player,or a digital video recorder. In further implementations, the computingdevice 1200 may be any other electronic device that processes data.

According to various embodiments, the present disclosure describes anumber of examples. Example 1 is a printed circuit board (PCB) assemblyfor absorbing a reflected electric signal, comprising a substrate, atleast one interconnect formed in the substrate to route an electricalsignal within the PCB, wherein the interconnect includes a connectingcomponent that is disposed on a surface of the PCB, and an absorbingmaterial that is disposed to be in direct contact with at least aportion of the connecting component to at least partially absorb aportion of the electrical signal.

Example 2 may include the subject matter of Example 1, and furtherspecifies that the interconnect comprises a transmission line thatincludes the connecting component, wherein a proximal end of thetransmission line that comprises the connecting component is disposed onthe surface of the PCB to form a port for the electrical signal passingthrough the transmission line, wherein the port is covered with theabsorbing material to form a first absorbing terminator to providesubstantial termination of the electrical signal.

Example 3 may include the subject matter of Example 2, and furtherspecifies that the first end of the transmission line is connected to atransmitter to transmit the electrical signal through the transmissionline, wherein the port comprises a second end of the transmission line.

Example 4 may include the subject matter of Example 3, and furtherspecifies that the transmission line is a first transmission line,wherein the interconnect further comprises a second transmission linedisposed in proximity to the first transmission line, wherein the secondtransmission line includes a second absorbing terminator comprising afirst end of the second transmission line covered with the absorbingmaterial.

Example 5 may include the subject matter of Example 4, and furtherspecifies that the first end of the second transmission line is disposedin proximity to the first end of the first transmission line, wherein asecond end of the second transmission line is connected to a receiver ofa signal caused by magnetic interference from the electric signalpassing through the first transmission line, wherein an arrangementincluding the first and second transmission lines is to enablemeasurements of far end cross-talk (FEXT) associated with the electricalsignal.

Example 6 may include the subject matter of Example 4, and furtherspecifies that the PCB assembly may further comprise a third absorbingterminator disposed at a second end of the second transmission line,wherein an arrangement including the first and second transmission linesis to enable measurements of FEXT return loss associated with theelectrical signal.

Example 7 may include the subject matter of Example 4, and furtherspecifies that a second end of the second transmission line is disposedin proximity to the first end of the first transmission line andconnected to a receiver of a signal caused by magnetic interference fromthe electric signal passing through the first transmission line, whereinan arrangement including the first and second transmission lines is toenable measurements of near end cross-talk (NEXT) associated with theelectrical signal.

Example 8 may include the subject matter of Example 1, and furtherspecifies that the electrical signal comprises a transmission signaltransmitted with a speed above a threshold of about 1 gigabits persecond (Gbps).

Example 9 may include the subject matter of Example 1, and furtherspecifies that the connecting component is a first connecting componentthat comprises a first connector slot to receive a corresponding firstconnecting element of a first computing component to be coupled with thePCB assembly.

Example 10 may include the subject matter of Example 9, and furtherspecifies that the PCB assembly may further comprise a second connectingcomponent that comprises a second connector slot to receive acorresponding second connecting element of a second computing componentto be coupled with the PCB assembly.

Example 11 may include the subject matter of Example 10, and furtherspecifies that the first computing component comprises a dummy module,wherein the first connecting element of the dummy module includes theabsorbing material, wherein the connecting component is covered with theabsorbing material when the first connecting element of the firstcomputing component is inserted into the first connector slot, whereinthe absorbing material is in direct contact with an inside portion ofthe first connector slot.

Example 12 may include the subject matter of Example 11, and furtherspecifies that the second computing component comprises a memory moduleto receive and store data comprising the electrical signal routed withinthe PCB, wherein the portion of the electrical signal to be at leastpartially absorbed by the first connecting component comprises areflected portion of the electrical signal.

Example 13 may include the subject matter of Example 12, and furtherspecifies that the memory module comprises a dual in-line memory module(DIMM).

Example 14 may include the subject matter of Examples 1 to 13, andfurther specifies that that the absorbing material has a dielectric losstangent of greater than one, for a frequency range of a resonantfrequency of a reflected portion of the electrical signal that is to beat least partially absorbed.

Example 15 may include the subject matter of Example 14, and furtherspecifies a relative dielectric constant is inversely proportionate tothe frequency of the reflected portion of the electric signal that is tobe at least partially absorbed.

Example 16 may include the subject matter of Example 15, and furtherspecifies that the dielectric loss tangent of the absorbing material issubstantially constant for the resonant frequency range of the frequencyof the reflected portion of the electric signal that is to be at leastpartially absorbed.

Example 17 is a method forming at least one interconnect on a printedcircuit board (PCB) assembly to route electrical signals within the PCB,the forming including disposing a connecting component of theinterconnect at least partially on a surface of the PCB and applying anabsorbing material to at least a portion of the connecting component,including providing a direct contact between the connecting componentand the absorbing material, to at least partially absorb a portion ofthe electrical signal.

Example 18 may include the subject matter of Example 17, and furtherspecifies that the disposing includes providing a first transmissionline, with a first proximal end of the first transmission linecomprising the connecting component forming a port for the electricalsignal passing through the first transmission line, wherein applying theabsorbing material includes covering the port with the absorbingmaterial to form a first absorbing terminator to provide substantialtermination of the electrical signal, the covering including retainingthe absorbing material in place by fastening or gluing.

Example 19 may include the subject matter of Example 18, and furtherspecifies that connecting a first end of the first transmission line toa transmitter to transmit the electrical signal through the firsttransmission line, wherein the first proximal end of the firsttransmission line including the port comprises a second end of the firsttransmission line; disposing a second transmission line in proximity tothe first transmission line, the disposing including forming a secondabsorbing terminator at a second proximal end of the second transmissionline by covering the second proximal end with the absorbing material,the covering including retaining the absorbing material in place byfastening or gluing, wherein an arrangement including the first andsecond transmission lines enables measurements of far end cross-talk(FEXT) and near end cross-talk (NEXT) associated with the electricalsignal.

Example 20 may include the subject matter of Examples 17 to 19, andfurther specifies that the disposing includes providing a firstconnector slot comprising the connecting component, the connector slotconfigured to receive a corresponding first connecting element of afirst computing component to be coupled with the PCB assembly.

Example 21 may include the subject matter of Example 20, and furtherspecifies that the first computing component comprises a dummy module,wherein the connecting element of the dummy module includes theabsorbing material, wherein applying an absorbing material includesinserting the connecting element of the dummy module into the firstconnector slot, to provide direct contact of the absorbing material withan inside portion of the first connector slot.

Example 22 may include the subject matter of Example 21, and furtherspecifies that the method may further comprise providing a secondconnecting component that comprises a second connector slot to receive acorresponding second connecting element of a second computing componentto be coupled with the PCB assembly, wherein the second computingcomponent comprises a memory module to receive and store data comprisingthe electrical signal routed within the PCB, wherein the portion of theelectrical signal to be at least partially absorbed by the firstconnecting component comprises a reflected portion of the electricalsignal.

Example 23 is a computing apparatus comprising processor, a memorycoupled with the processor and a printed circuit board (PCB) assemblycoupled with the processor and memory, the PCB assembly comprising: asubstrate; at least one interconnect formed in the substrate to route anelectrical signal within the PCB, wherein the interconnect includes aconnecting component that is disposed on a surface of the PCB; and anabsorbing material that is disposed to be in direct contact with atleast a portion of the connecting component to at least partially absorba portion of the electrical signal.

Example 24 may include the subject matter of Example 23, and furtherspecifies that the interconnect comprises a transmission line thatincludes the connecting component, wherein a proximal end of thetransmission line that comprises the connecting component is disposed onthe surface of the PCB to form a port for the electrical signal passingthrough the transmission line, wherein the port is covered with theabsorbing material to form a first absorbing terminator to providesubstantial termination of the electrical signal.

Example 25 may include the subject matter of Examples 23 to 24, andfurther specifies that the connecting component is a first connectingcomponent that comprises a first connector slot to receive acorresponding first connecting element of a first computing component tobe coupled with the PCB assembly, wherein the computing apparatusfurther comprises a second connecting component that includes a secondconnector slot to receive a corresponding second connecting element of asecond computing component to be coupled with the PCB assembly, whereinthe first computing component comprises a dummy module, wherein theconnecting element of the dummy module includes the absorbing materialto cover the connecting component when the first computing component isinserted into the first connector slot.

Various embodiments may include any suitable combination of theabove-described embodiments including alternative (or) embodiments ofembodiments that are described in conjunctive form (and) above (e.g.,the “and” may be “and/or”). Furthermore, some embodiments may includeone or more articles of manufacture (e.g., non-transitorycomputer-readable media) having instructions, stored thereon, that whenexecuted result in actions of any of the above-described embodiments.Moreover, some embodiments may include apparatuses or systems having anysuitable means for carrying out the various operations of theabove-described embodiments.

The above description of illustrated implementations, including what isdescribed in the Abstract, is not intended to be exhaustive or to limitthe embodiments of the present disclosure to the precise formsdisclosed. While specific implementations and examples are describedherein for illustrative purposes, various equivalent modifications arepossible within the scope of the present disclosure, as those skilled inthe relevant art will recognize.

These modifications may be made to embodiments of the present disclosurein light of the above detailed description. The terms used in thefollowing claims should not be construed to limit various embodiments ofthe present disclosure to the specific implementations disclosed in thespecification and the claims. Rather, the scope is to be determinedentirely by the following claims, which are to be construed inaccordance with established doctrines of claim interpretation.

What is claimed is: 1-25. (canceled)
 26. An apparatus comprising: aprinted circuit board (PCB) comprising at least one transmission line toroute an electrical signal within the PCB, wherein at least one end ofthe transmission line is coupled to a connecting component thatcomprises a connector slot disposed on a surface of the PCB; and aconnecting element inserted in the connector slot, wherein at least asurface of the connecting element that faces the connector slot iscovered with an absorbing material in contact with at least a portion ofthe connector slot, to at least partially absorb a portion of theelectrical signal.
 27. The apparatus of claim 26, wherein the electricalsignal comprises a transmission signal transmitted at a frequencybetween 5 and 7 GHz.
 28. The apparatus of claim 26, wherein theconnecting component is a first connecting component, wherein theconnector slot is a first connector slot, wherein the connecting elementis a first connecting element of a first computing component coupledwith the apparatus.
 29. The apparatus of claim 28, further comprising asecond connecting component coupled with the transmission line, whereinthe second connecting component comprises a second connector slot toreceive a corresponding second connecting element of a second computingcomponent coupled with the apparatus.
 30. The apparatus of claim 29,wherein the first connecting component comprises a dual in-line memorymodule (DIMM) connector, and wherein the first computing componentcomprises a dummy module.
 31. The apparatus of claim 29, wherein thesecond connecting component comprises a dual in-line memory module(DIMM) connector, wherein the second computing component comprises amemory module to receive and store data indicated by the electricalsignal routed within the PCB, and wherein the portion of the electricalsignal to be at least partially absorbed by the first connecting elementcomprises a reflected portion of the electrical signal.
 32. Theapparatus of claim 31, wherein a dielectric loss tangent of theabsorbing material is greater than one, for a frequency range of aresonant frequency of the reflected portion of the electrical signal.33. The apparatus of claim 32, wherein the dielectric loss tangent ofthe absorbing material is substantially constant for the resonantfrequency range of the frequency of the reflected portion of theelectrical signal.
 34. The apparatus of claim 31, wherein a relativedielectric constant of the absorbing material is inversely proportionateto a frequency of the reflected portion of the electrical signal.
 35. Anapparatus, comprising: a connecting element insertable in a connectorslot disposed on a surface of a printed circuit board (PCB), wherein atleast a surface of the connecting element that faces the connector slotis covered with an absorbing material in contact with at least a portionof the connector slot, to at least partially absorb a portion of anelectrical signal routed through a transmission line that is coupledwith the connector slot and disposed inside the PCB.
 36. The apparatusof claim 35, further comprising a dummy module, wherein the connectingelement is coupled with the dummy module.
 37. The apparatus of claim 35,wherein the connector slot comprises a dual in-line memory module (DIMM)connector.
 38. The apparatus of claim 35, wherein a dielectric losstangent of the absorbing material is greater than one, for a frequencyrange of a resonant frequency of a portion of the electrical signalreflected by the connector slot.
 39. The apparatus of claim 38, whereinthe dielectric loss tangent of the absorbing material is substantiallyconstant for the resonant frequency range of the frequency of thereflected portion of the electrical signal.
 40. The apparatus of claim35, wherein a relative dielectric constant of the absorbing material isinversely proportionate to a frequency of the reflected portion of theelectrical signal.
 41. A method, comprising: providing a connectingelement insertable in a connector slot disposed on a surface of aprinted circuit board (PCB); and applying an absorbing material to atleast a surface of the connecting element that faces the connector slot,to at least partially absorb a portion of an electrical signal routedthrough a transmission line that is coupled with the connector slot anddisposed inside the PCB, wherein applying an absorbing material includesdirectly covering the surface of the connecting element with theabsorbing material.
 42. The method of claim 41, wherein providing aconnecting element includes providing a dummy module insertable in theconnector slot, wherein the dummy module includes the connectingelement.
 43. The method of claim 41, wherein a dielectric loss tangentof the absorbing material is greater than one, for a frequency range ofa resonant frequency of a portion of the electrical signal reflected bythe connector slot.
 44. The method of claim 43, wherein the dielectricloss tangent of the absorbing material is substantially constant for theresonant frequency range of the frequency of the reflected portion ofthe electrical signal.
 45. The method of claim 41, wherein a relativedielectric constant of the absorbing material is inversely proportionateto a frequency of the reflected portion of the electrical signal.